Construction of a modified carbon nanotube composite sensor Based on N-quinoline-2-carboxamido-8-aminoquinoline

Potentiometric sensors have shown to be very effective tools for analysis of a wide variety of metal ions. Among them, carbon paste electrods (CPEs) have attracted interest as a result of their improved renewability, stable response, and low ohmic resistance compared to membrane electrodes. N-quinoline-2 carboxamido-8-aminoquinoline (QCA) seemed to be a suitable ion carrier for metal ions due to the presence of intermediate donating N atoms in its structur. Preliminary solution study shows the selectivity of (QCA) toward Ho3+ (III) ions in comparison of other common cations, including alkali, alkaline earth, transition and heavy metal ions. To have a long – term stable electrode for potentiometric uses, (QCA) was applied as ionophore in preparation of a nano-composite carbone paste electrode. The carbon paste electrode composed of 2% MWCNTs, 0.3 % Nano silica, 25% Paraffin oil, 1% QCA, and 71.7% Graphite Powder showed the best response. The proposed sensor exhibits a Nerstian slope of 19.6±0.4 mv decad-1 toward Ho3+ ions in the range of 1.0×10-8 M-1.0×10-2 M and detection limit of 7.3 × 10-9 M .